Do NOT use any sub trim or trim on teh rudder. What you need to do is adjust the linkage rod for the tail. make small adjustments to it. Also, you need to raise your tail gain up until you get a wag, then back it down 5%. This will also help with the tail drift. I'm thinking more so than the linkage rod quite honestly.
If you want a perfect tail, you need to setup some kind of flat throttle curve (in normal mode, something like 0 40 75 75 75), then set your Gyro to Rate Mode, or a red light on the 3GX (if that is what you are using). In rate mode when you are in the air, you should adjust the linkage rod so that you can hover with no tail drift. This will get your tail blades set perfectly. However, once you are done with that, you MUST go back into the rudder setup menu on the gyro and reset your endpoints since you have changed them. You can also do all of this in DIR mode of the gyro, but you have to go into that mode, make the adjustment with sub trim (I know, I said not to, but this is the ONLY way you cna do it), adn once you are done making the adjustment, unplug the battery, reinitialize the gyro and try the hover again (or flight).
Hope this helps.